Enhanced Prediction of CH4 Adsorption in Coal at High Pressure and Temperature

The study of CH4 adsorption behavior in coal under high-temperature and high-pressure conditions is essential for accurately estimating gas content in deep coal reservoirs. However, conducting adsorption experiments under such conditions poses significant challenges. This study aims to develop a feasible method for predicting high-temperature and high-pressure adsorption data based on low-temperature and low-pressure results. By comparing the predictive performance of three previously used methods for high-temperature adsorption, it was determined that the adsorption heat method effectively predicts CH4 adsorption isotherms using only three sets of low-temperature data, with an average relative percent error (% ARD) of less than 10%. In contrast, both the adsorption potential method and Henry's constant method require at least four data sets to achieve comparable prediction accuracy. The traditional method for predicting high-pressure adsorption data shows unreliable results unless data above 15 MPa are utilized to establish the prediction model. In contrast, the novel method proposed in this study enables the estimation of high-pressure adsorption data using only data below 5 MPa, with a % ARD of less than 6.89%. These findings can significantly contribute to evaluating adsorption gas content in deep CBM reservoirs.